Mechanisms for activation and subsequent removal of cytosolic Ca2+ in bradykinin-stimulated neuronal and glial cell lines.
Mechanisms for activation and for removal of cytosolic Ca2+ after stimulation with bradykinin were investigated in two neural cell lines by measuring cytosolic Ca2+ activity and 45Ca2+ fluxes. In the neuronal (neuroblastoma x glioma hybrid) and in the glial (rat glioma) cell lines, the transient, bradykinin-induced rise in cytosolic Ca2+ activity (determined by fura-2 or indo-1 fluorescence) was blocked by a bradykinin B2 receptor antagonist. Ca2+ ionophores (ionomycin and 4-Br-A23187) caused a comparable transient rise in cytosolic Ca2+ activity. After addition of ionophores, the Ca2+ response to bradykinin was reduced or completely blocked in both cell lines. At the concentrations used, the ionophores primarily depleted intracellular Ca2+ stores and prevented refilling of the stores. Thus, the bradykinin-induced rise of cytosolic Ca2+ activity seems to be mostly due to Ca2+ release from internal stores. In the neuronal but not in the glial cell line, a brief stimulation by bradykinin of 45Ca2+ uptake was followed by a long-lasting inhibition below control values. Thus, in the neuronal cells bradykinin presumably blocks Ca2+ channels by a readily reversible, pertussis toxin-insensitive mechanism. Excess cytosolic Ca2+ of the bradykinin-stimulated cells is mostly not resequestered into the internal Ca2+ pool accessible to bradykinin, but is mainly extruded through the plasma membrane, as indicated by (i) stimulation of 45Ca2+ release by bradykinin, (ii) quick reduction by bradykinin of cellular 45Ca2+ content of cells preequilibrated with 45Ca2+, and (iii) diminution of the ionophore-inducible Ca2+ response after the addition of bradykinin.
Reiser
G
G
Physiologisch Chemisches Institut, Universität Tübingen, Federal Republic of Germany.
Binmöller
F J
FJ
Donié
F
F
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009423:Nervous System Neoplasms / Q000378:metabolism / Q000473:pathology; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D051381:Rats; D014407:Tumor Cells, Cultured / Q000187:drug effects*
D001920:Bradykinin; D002118:Calcium